LONDON — Motorola, Inc. has released initial findings from in depth trials it has been conducting into how best to deploy HSDPA (High Speed Downlink Packet Access) enabled cellular networks in Europe.
The company says the findings from the multiple user, outdoor trials will help operators determine how to best deploy HSDPA. It stresses that initial user perception in the adoption of mobile broadband will be critical, and the aim for operators must be to provide a performance similar to fixed broadband.
Perhaps the most important of the three guidelines from the various trials is the need to supply sufficient processing power so as to reduce latency.
While HSDPA is great at enhancing the data rates of existing cellular networks, the Motorola studies show the technology can be prone to delays when using applications such as web browsing. Caused by a mechanism known as ‘state switching’, this effectively moves a user from a high to a low speed state based on user activity without the user being aware.
It can cause delays of seconds as the radio network transitions back from a slow to a fast state, and will be unacceptable for services marketed as ‘mobile broadband’. The solution, according to Motorola is to avoid switching users down from a high to a low speed state regardless of user activity. As HSDPA enables radio resources to be dynamically shared between users it is important to reduce such state switching.
However, the company notes that this scheduling requires intensive computer processing capabilities at the base station. “Network operators should ensure that they have sufficient processing power at the base stations to schedule the highest possible number of calls at launch of the HSDPA service”, the study suggests.
Another vital aspects for a successful HSDPA roll-out is to adopt key handset functionality for improved mobile performance.
The performance of HSDPA is heavily dependent on device or handset capability. A signal processing function known as an equaliser enhances performance when the user is moving. Motorola says initial trial results demonstrate an increase in data rates of as much as 40 percent for devices that support equalisation. Only a few device manufacturers currently claim to have equaliser functionality.
The trials also show that video streaming performance degrades when a relatively modest number of users are active. “As little as four active users are sufficient to cause video streaming to freeze if scheduling priorities are not set properly,” the company says.
To compensate for this, operators must actively prioritise video over other services or provide more capacity. Operators could defer video services on HSDPA to a later stage, but as video services consume a large amount of UMTS capacity they should be moved to HSDPA for improved efficiency.